The present invention relates to a leadframe as a land grid array (LGA) in which multiple lands are arranged in columns and rows of external terminals exposed on the bottom of a package. This invention also relates to a resin-molded semiconductor device including the leadframe, a method of making the leadframe and a method for manufacturing the device.
In recent years, to catch up with rapidly advancing downsizing and performance enhancement of electronic units, it has become increasingly necessary to assemble semiconductor components at a higher and higher density. To meet this demand, a resin-molded semiconductor device, formed by molding a semiconductor chip and leads together with a resin encapsulant, has its size and thickness reduced noticeably. In parallel with this downsizing trend, the number of pins required for a single electronic unit is also increasing day after day.
Hereinafter, a known leadframe for use in a resin-molded semiconductor device will be described with reference to the drawings.
FIG. 12 illustrates a plan view of a known leadframe. The leadframe 100 shown in FIG. 12 is for use in a quad flat package (QFP) in which external pins extend outward from the four side faces of a rectangular parallelepiped package. As shown in FIG. 12, the leadframe 100 includes frame rail 101, rectangular die pad 102, inner leads 103 and outer leads 104. The die pad 102 is located at the center of the frame rail 101. The inner end of each inner lead 103 faces an associated side of the die pad 102 and the respective inner ends of the inner leads 103 are spaced apart from the sides of the die pad 102. The inner end of each outer lead 104 is connected to the outer end of the associated inner lead 103 while the outer end of each outer lead 104 is connected to the frame rail 101. The outer leads 104 are joined together by a tie bar 105 for preventing the overflow of a resin encapsulant during a resin molding process. And the die pad 102 is supported at the four corners by support pins 106 that are connected to the tie bar 105.
In FIG. 12, the members existing inside the dashed-line region 109 will be molded together by a resin encapsulant. Although just a part of the leadframe 100 for one device is illustrated in FIG. 12, the leadframe 100 actually has many other parts that each have the pattern shown in FIG. 12 and that are arranged in columns and rows.
FIG. 13 illustrates a cross-sectional structure for a resin-molded semiconductor device including the leadframe 100. In FIG. 13, each component also shown in FIG. 12 is identified by the same reference numeral.
As shown in FIG. 13, a semiconductor chip 107 is bonded onto the die pad 102 using some adhesive or solder. The semiconductor chip 107 is electrically connected to the inner leads 103 using metal fine wires 108. The die pad 102, semiconductor chip 107 on the die pad 102, metal fine wires 108 and inner leads 103 are molded together with a resin encapsulant 109A. In this case, the bottom of the die pad 102 is completely buried in the resin encapsulant 109A. The outer leads 104 extend outward from the side faces of the resin encapsulant 109A parallelly to the surface of the die pad 102 on which the chip 107 has been mounted. Also, the outer leads 104 have been bent downward so that this package can be surface-mounted onto a motherboard.
As described above, the number of components that should be integrated together within a single semiconductor chip 107, or the number of external electrodes (or pins) per chip, has been on the rise these days. Thus, the number of outer leads 104 should also be increased to catch up with this latest trend. That is to say, the number of inner leads 103, which are joined to the outer leads 104, should also be increased to cope with such an implementation. However, the width of the inner (or outer) leads 103 or 104 has a patternable limit. Accordingly, if the number of inner (or outer) leads 103 or 104 was further increased, the overall size of the leadframe 100 should also increase. This is not allowable because the increase in size of the leadframe 100 is incompatible with the recent downsizing trend. On the other hand, if the width of the inner or outer leads 103 or 104 were reduced, then it would be much more difficult to form the leadframe 100 in its desired shape.
To cope with these problems, face-bonded semiconductor devices, such as ball grid array (BGA) and land grid array (LGA) types, are also available recently. In semiconductor devices of these types, a semiconductor chip is mounted onto the non-circuitry side of a carrier (e.g., a printed wiring board), including ball or land electrodes on its back surface, and is electrically connected to these electrodes.
A semiconductor device of the BGA or LGA type is then mounted onto a motherboard so that its back surface faces the principal surface of the motherboard. And then the external electrodes (i.e., the ball or land electrodes), exposed on the back surface of the device, are directly connected electrically to the electrodes on the motherboard.
The BGA- or LGA-type semiconductor device, however, uses a multilayer carrier (or wiring board) in which ceramic or plastic layers have been stacked. Accordingly, the fabrication process thereof is overly complicated and the fabrication cost thereof is far from reasonable.
Also, it is hard to apply a method for manufacturing the known resin-molded semiconductor device shown in FIGS. 12 and 13 as it is to forming a semiconductor device of the BGA or LGA type. The reason is as follows. In the manufacturing process, part of a metal plate, including portions to be lands as external electrodes, should be connected to the frame rail with some joining/supporting members before the lands are formed. Accordingly, where lands should be arranged in three or more rows, the device of the BGA- or LGA-type device cannot be so small.
In addition, according to the method for manufacturing the known resin-molded semiconductor device shown in FIGS. 12 and 13, the device cannot be mounted onto the motherboard so accurately as in manufacturing a face-bonded semiconductor device of the BGA or LGA type. As described above, the beam-like outer leads 104 shown in FIG. 12 extend linearly outward from the sides of the resin encapsulant 109A just after the members of the device have been molded. Accordingly, the outer leads 104 should be bent downward so that the far end of each outer lead 104 has its bottom located at least no higher than the back surface of the resin encapsulant 109A. And in this bending process step, the outer leads 104 cannot be bent so uniformly and the far ends of the outer leads 104 are likely located at various levels.
It is therefore an object of the present invention to make a smaller leadframe, including lands arranged in multiple (three or more, in particular) rows, out of a single-layer metal plate easily enough to manufacture a downsized resin-molded semiconductor device using the leadframe.
To achieve this object, according to the present invention, a plurality of lands are arranged in columns and rows between a frame rail and a die pad, and the lands and frame rail get retained by a lead retaining member on the upper and/or lower surface(s) thereof.
Specifically, a first inventive leadframe includes: a frame rail; a die pad, disposed inside the frame rail, for mounting a semiconductor chip thereon; and a plurality of internal inner leads, which are disposed to surround the die pad and each of which has a convex portion on the bottom thereof. The frame rail and the internal inner leads are retained by a lead retaining member on their upper and/or lower surface(s).
In the first leadframe, the internal inner leads, each having a convex portion to be an external terminal (i.e., land) on its bottom, and the frame rail are retained by a lead retaining member on their upper and/or lower surface(s). Accordingly, the internal inner leads do not have to be supported by the frame rail. That is to say, there is no need to provide any joining/supporting member for joining the internal inner leads and the frame rail together. For that reason, even if the lands are arranged in three or more rows between the frame rail and the die pad, the frame rail still can be formed in a smaller size. Thus, a downsized leadframe, including lands arranged in multiple rows, can be made out of a single-layer metal plate easily.
In one embodiment of the first leadframe, at least some of the internal inner leads preferably have their convex portions insolated from each other. And each said isolated convex portion is preferably surrounded with an elevated (or burred) portion, which extends vertically to the bottom of the internal inner lead, so that the top of the elevated portion is lower than the top of the convex portion. Suppose the internal inner lead portions are supported by joining/supporting members extending from the die pad in an early stage of a leadframe manufacturing process. And if the burred portions, which will be formed when the joining/supporting members are cut off with a stamper (or die punch) in a subsequent process step, have their top positioned lower than that of the convex portions, then only the top of the convex portions will be exposed out of the resin encapsulant at the molding process step. Accordingly, the leakage current can be eliminated and a semiconductor device including the first inventive leadframe will not operate erroneously.
In another embodiment, the first leadframe preferably further includes a plurality of external inner leads, which are disposed between the frame rail and the internal inner leads to extend inward from the frame rail and each of which has a convex portion on the bottom thereof. Then, a leadframe, including lands arranged in multiple rows, can be formed just as intended.
A second inventive leadframe includes: a frame rail; a die pad, disposed inside the frame rail, for mounting a semiconductor chip thereon; and a plurality of inner leads disposed between the frame rail and the die pad. The frame rail and the inner leads are retained by a lead retaining member on their upper and/or lower surface(s). Each of the inner leads has a convex portion on the bottom thereof. The convex portions are spaced apart from each other. And at least some of the convex portions are isolated from adjacent ones of the convex portions, while the other convex portions are supported by joining/supporting members.
In the second leadframe, the frame rail and the inner leads are retained by the lead retaining member on their upper and/or lower surface(s). Accordingly, the isolated convex portions to be lands do not have to be supported by the frame rail. That is to say, there is no need to provide the joining/supporting members for joining the inner leads, each including the isolated convex portion, and the frame rail together. For that reason, even if the lands are arranged in three or more rows between the frame rail and the die pad, the frame rail still can be formed in a smaller size. Thus, a downsized leadframe, including lands arranged in multiple rows, can be made out of a single-layer metal plate easily.
In one embodiment of the second leadframe, each said isolated convex portion is preferably surrounded with an elevated portion, which extends vertically to the bottom of the inner lead, so that the top of the elevated portion is lower than the top of the convex portion.
In another embodiment of the first or second leadframe, the die pad preferably has a concave portion on the bottom thereof. Then, water much less likely enters the resin encapsulant because the chip is more distant from the bottom of the resin encapsulant. In addition, the stress applied downward onto the chip from over the resin encapsulant can also be reduced because the resin, protecting the chip from under its bottom, increases its thickness.
A third inventive leadframe includes: a frame rail; a die pad, disposed inside the frame rail, for mounting a semiconductor chip thereon; a plurality of lands disposed between the frame rail and the die pad; and a plurality of inner leads for electrically connecting some of the lands together. The frame rail and the lands are retained by a lead retaining member on the upper and/or lower surface(s) thereof. Each said inner lead connects associated ones of the lands together between two adjacent ones of the lands. The top of the inner lead is almost as high as the top of the two adjacent lands, while the bottom of the inner lead is higher than the bottom of the two adjacent lands. And when taken vertically to a direction in which the inner leads extend, each said land has such a cross-sectional shape that an upper part of the land, each side face of which faces a side face of associated one of the inner leads, has a decreased width.
In the third leadframe, the inner leads, each connecting associated ones of the lands together between two adjacent ones of the lands, are provided. But each of the lands has a cross-sectional shape with an upwardly decreasing width. Accordingly, each of the inner leads is located between the respective upper parts of the two adjacent lands with the decreased width. That is to say, the space between the side faces of the two adjacent lands is greater in the upper part thereof than in the lower part thereof. For that reason, the inner leads can be disposed between the lands without reducing the size of the lands or the width of the inner leads.
A first inventive leadframe making method includes the step of a) forming a frame rail, a die pad, multiple internal inner lead portions and multiple external inner lead portions out of a single metal plate. The die pad is supported by joining/supporting members that extend inward from the frame rail. The internal inner lead portions are connected to the die pad so as to surround the die pad. And the external inner lead portions are connected to the frame rail. The method further includes the step of b) forming convex portions in respective parts of the internal and external inner lead portions so that each said convex portion formed in that part of associated one of the internal inner lead portions is spaced apart from the die pad and that each said convex portion formed in that part of associated one of the external inner lead portions is spaced apart from the frame rail. The convex portions are formed on respective surfaces of the internal and external inner lead portions opposite to a surface of the die pad on which a chip will be mounted. The method further includes the step of c) placing a lead retaining member on respective surfaces of at least the internal inner lead portions and the frame rail and thereby getting the internal inner lead portions and the frame rail retained by the retaining member. The surfaces on which the retaining member is placed are either the same as, or opposite to, the surface of the die pad on which the chip will be mounted. And the method further includes the step of d) removing, from at least some of the internal inner lead portions, respective parts thereof located between the convex portions and the die pad, thereby forming internal inner leads that have been selectively isolated from the die pad.
In the first leadframe making method, at least the internal inner lead portions and the frame rail are retained by the lead retaining member on their respective surfaces that are the same as, or opposite to, the surface of the die pad on which the chip will be mounted. Accordingly, even if the internal inner lead portions are selectively isolated from the die pad after that by a cutting or etching process, the isolated internal inner leads will not drop off from the frame rail. Thus, the first leadframe of the present invention, for which no joining/supporting members are needed to join and support the internal inner leads and the frame rail together, can be obtained.
In one embodiment of the first leadframe making method, the convex portions may be formed in the step b) by etching away a part of the metal plate located between the part of each said internal inner lead portion in which the associated convex portion will be formed and the die pad and another part of the metal plate located between the part of each said external inner lead portion in which the associated convex portion will be formed and the frame rail. Those parts may be etched away from a surface of the metal plate opposite to the surface of the die pad on which the chip will be mounted. Then, the convex portions to be the lands can be formed in a desired small size.
In an alternative embodiment, the convex portions may be formed in the step b) by pressing a part of the metal plate located between the part of each said internal inner lead portion in which the associated convex portion will be formed and the die pad and another part of the metal plate located between the part of each said external inner lead portion in which the associated convex portion will be formed and the frame rail. Those parts may be pressed on a surface of the metal plate opposite to the surface of the die pad on which the chip will be mounted. Then, the convex portions to be the lands can be easily formed just as intended.
In still another embodiment, the convex portions may be isolated in the step d) from the die pad by cutting off the respective parts of the internal inner lead portions located between the convex portions and the die pad using cutting means. Then, the convex portions can be isolated from the die pad easily and the lands can be formed as the convex portions that have been isolated from each other.
A second inventive leadframe making method includes the step of a) forming a frame rail, multiple inner lead portions and a die pad out of a single metal plate. The inner lead portions are supported by a first group of joining/supporting members that extend inward from the frame rail, and are joined together by a second group of joining/supporting members. The method further includes the step of b) forming convex portions on a surface of the inner lead portions so that the convex portions are spaced apart from each other. The surface is opposite to a surface of the die pad on which a chip will be mounted. The method further includes the step of c) placing a lead retaining member on respective surfaces of the inner lead portions and the frame rail and thereby getting the inner lead portions and the frame rail retained by the retaining member. The surfaces on which the retaining member is placed may be either the same as, or opposite to, the surface of the die pad on which the chip will be mounted. And the method further includes the step of d) selectively isolating the inner lead portions by removing, from at least some of the joining/supporting members of the second group for the inner lead portions, respective parts thereof located between adjacent ones of the convex portions or between one of the convex portions and the die pad that are adjacent to each other.
In the second leadframe making method, the inner lead portions and the frame rail are retained by the lead retaining member on their respective surfaces that are the same as, or opposite to, the surface of the die pad on which the chip will be mounted. Accordingly, even if the inner lead portions are selectively isolated from the die pad after that by a cutting or etching process, the isolated inner leads or die pad will not drop off from the frame rail. Thus, the second leadframe of the present invention, for which no joining/supporting members are needed to join and support the inner leads, die pad and frame rail together, can be obtained.
In one embodiment of the second leadframe making method, the convex portions may be formed in the step b) by etching away a part of each said joining/supporting member of the second group. The part to be etched may be located either between the parts of the associated inner lead portions where the convex portions will be formed or between the part of the associated inner lead portion where the convex portion will be formed and the die pad. Also, the part may be etched away from a surface of the joining/supporting members of the second group opposite to the surface of the die pad on which the chip will be mounted.
In an alternative embodiment, the convex portions may be formed in the step b) by pressing a part of each said joining/supporting member of the second group. The part to be pressed may be located either between the parts of the associated inner lead portions where the convex portions will be formed or between the part of the associated inner lead portion where the convex portion will be formed and the die pad. Also, the part may be pressed on a surface of the joining/supporting members of the second group opposite to the surface of the die pad on which the chip will be mounted.
In still another embodiment, a part of each selected joining/supporting member of the second group, which part is located either between associated ones of the convex portions or between associated one of the convex portions and the die pad, may be cut off in the step d) with cutting means, thereby isolating the convex portions from each other or from the die pad.
In yet another embodiment of the first or second leadframe making method, the cutting means preferably has a cut face, which is substantially parallel to respective upper surfaces of the convex portions and the die pad. Then, no burred portion will be formed around the convex portion, for example. Also, if the joining/supporting members are cut off by a punching process like this, then some debris will be made. However, if the debris is received by the lead retaining member, the debris will not affect the manufacturing process.
A third inventive leadframe making method includes the step of a) forming a frame rail, lands, inner leads and a die pad out of a single metal plate. The lands are supported by joining/supporting members extending inward from the frame rail and are joined together so as to be spaced apart from each other. The inner leads electrically connect some of the lands together. And the die pad has a surface on which a chip will be mounted. The method further includes the step of b) placing a lead retaining member on respective surfaces of the lands and the frame rail and thereby getting the lands and the frame rail retained by the retaining member. The surfaces on which the retaining member is placed may be either the same as, or opposite to, the surface of the die pad on which the chip will be mounted. The method further includes the step of c) removing, from at least some of the joining/supporting members, respective parts thereof located between adjacent ones of the lands, thereby selectively isolating the lands.
In the third leadframe making method, the lands and frame rail are retained by the lead retaining member on their upper and/or lower surface(s). Accordingly, even if the resultant leadframe includes not only the lands but also the inner leads for electrically connecting some of the lands together, neither the lands nor the inner leads will drop off from the frame rail. Thus, a small-sized leadframe, including lands arranged in multiple rows, can be easily made out of a single-layer metal plate.
In one embodiment of the third leadframe making method, the step a) preferably includes the step of forming the inner leads out of the joining/supporting members between the lands by etching away respective parts of the metal plate from a surface thereof, on which the chip will be mounted, to approximately half the thickness of the metal plate while masking other parts of the metal plate that will be respective center portions of the lands extending in parallel to the associated joining/supporting member and also masking still other parts of the metal plate that will be the inner leads located between the associated lands. The step a) preferably further includes the step of etching away yet other parts of the metal plate from another surface thereof, opposite to the surface on which the chip will be mounted, while those parts of the metal plate to be the lands masked on the opposite surface so that the lands and the inner leads are isolated from each other.
Then, each of the lands will have a cross-sectional shape with an upwardly decreasing width and each of the inner leads, formed between adjacent lands, will have its top positioned approximately as high as that of the lands and its bottom positioned higher than that of the lands. Thus, the third inventive leadframe can be formed just as intended.
A first inventive resin-molded semiconductor device includes: a die pad; a semiconductor chip bonded onto the die pad; a plurality of inner leads, which are arranged in three or more columns and rows between the die pad and one side of the device to surround the die pad and at least some of which are isolated; and a resin encapsulant that molds the chip, the die pad and the inner leads together so as to expose a surface of the inner leads opposite to a surface of the die pad onto which the chip has been bonded. The die pad and the inner leads are made of a single metal plate.
The first resin-molded semiconductor device can be formed using a leadframe that has been shaped out of a single-layer metal plate to include lands arranged in multiple (e.g., three or more, in particular) rows.
In one embodiment of the first device, each said inner lead preferably has a convex portion on the bottom thereof. The top of the convex portion is preferably exposed out of the resin encapsulant. An elevated portion, extending vertically to the bottom of the inner lead so that the top of the elevated portion is lower than the top of the convex portion, is preferably formed around the convex portion. Suppose the inner lead portions are supported by joining/supporting members extending from the frame rail in an early stage of a leadframe manufacturing process. Even so, in this device, the burred portions, which will be formed when the joining/supporting members are cut off with a stamper (or die punch) in a subsequent process step, should have their top positioned lower than that of the convex portions. Accordingly, only the top of the convex portions will be exposed out of the resin encapsulant at the molding process step.
In another embodiment of the first device, the die pad preferably has a concave portion on the bottom thereof. Then, water much less likely enters the resin encapsulant because the chip is more distant from the bottom of the resin encapsulant. In addition, the stress applied downward onto the chip from over the resin encapsulant can also be reduced because the resin, protecting the chip from under its bottom, increases its thickness.
In still another embodiment, none of the inner leads should be exposed out of the side faces of the resin encapsulant. Then, the leakage current, which otherwise might flow through the side faces of this resin-molded semiconductor device when the device is mounted onto a motherboard, can be eliminated.
A second inventive resin-molded semiconductor device includes: a die pad; a semiconductor chip bonded onto the die pad; a plurality of lands disposed around the die pad, at least some of the lands being isolated; a plurality of inner leads, disposed around the die pad, for electrically connecting some of the lands together; and a resin encapsulant that molds the chip, the die pad, the lands and the inner leads together so as to expose a surface of the lands opposite to a surface of the die pad onto which the chip has been bonded. Each said inner lead connects associated ones of the lands together between two adjacent ones of the lands. The top of the inner lead is almost as high as the top of the two adjacent lands, while the bottom of the inner lead is higher than the bottom of the two adjacent lands. And when taken vertically to a direction in which the inner leads extend, each said land has such a cross-sectional shape that an upper part of the land, each side face of which faces a side face of associated one of the inner leads, has a decreased width.
In the second resin-molded semiconductor device, each of the inner leads is located between the respective upper parts of the two adjacent lands with the decreased width. That is to say, the space between the side faces of the lands is greater in the upper parts thereof than in the lower parts thereof. For that reason, the inner leads can be disposed between the lands without reducing the size of the lands or the width of the inner leads.
A first inventive method for manufacturing a resin-molded semiconductor device includes the step of a) forming frame rails, die pads and multiple sets of internal and external inner lead portions out of a single metal plate. Each said die pad is supported by joining/supporting members that extend inward from associated one of the frame rails. Each said set of internal inner lead portions are connected to associated one of the die pads so as to surround the die pad. And each said set of external inner lead portions are connected to associated one of the frame rails. The method further includes the step of b) forming convex portions in respective parts of the internal and external inner lead portions so that each said convex portion formed in that part of associated one of the internal inner lead portions is spaced apart from the associated die pad and that each said convex portion formed in that part of associated one of the external inner lead portions is spaced apart from the associated frame rail. The convex portions are formed on respective surfaces of the internal and external inner lead portions opposite to an upper surface of the die pads on which semiconductor chips will be bonded. The method further includes the step of c) placing a lead retaining member on respective surfaces of at least the internal inner lead portions and the frame rails and thereby getting the internal inner lead portions and the frame rails retained by the retaining member. The surfaces on which the retaining member is placed may be either the same as, or opposite to, the upper surface of the die pads on which the chips will be bonded. The method further includes the step of d) removing, from at least some of the internal inner lead portions, respective parts thereof located between the convex portions and the associated die pads, thereby forming internal inner leads that have been selectively isolated from the die pads and obtaining a leadframe with the lead retaining member. The method further includes the steps of: e) bonding the chips onto the upper surface of the die pads of the leadframe; and f) electrically connecting the chips to the isolated internal inner leads and the external inner lead portions using metal fine wires. If the lead retaining member has been placed on the surface of the leadframe on which the chips have been bonded, the method further includes the step of g) removing the lead retaining member from the surface of the leadframe on which the chips have been bonded. The method further includes the step of h) molding the chips, the die pads, the internal inner leads and the external inner lead portions together with a resin encapsulant so that the convex portions of the internal inner leads and the external inner lead portions have their top exposed. If the lead retaining member has been placed on another surface of the leadframe opposite to the surface thereof on which the chips have been bonded, the method further includes the step of i) removing the lead retaining member from the opposite surface of the leadframe. And the method further includes the step of j) dividing the leadframe, along with the members assembled thereon, into multiple packages so that each said package includes at least one of the chips.
According to the first inventive manufacturing method, the first inventive resin-molded semiconductor device can be formed just as intended by using the first inventive leadframe.
In one embodiment of the first manufacturing method, the convex portions may be formed in the step b) by etching away a part of the metal plate located between the part of each said internal inner lead portion in which the associated convex portion will be formed and the associated die pad and another part of the metal plate located between the part of each said external inner lead portion in which the associated convex portion will be formed and the associated frame rail. Those parts may be etched away from a surface of the metal plate opposite to the surface of the leadframe on which the chips will be bonded. Then, the convex portions to be the lands can be formed in a desired small size.
In an alternative embodiment, the convex portions may be formed in the step b) by pressing a part of the metal plate located between the part of each said internal inner lead portion in which the associated convex portion will be formed and the associated die pad and another part of the metal plate located between the part of each said external inner lead portion in which the associated convex portion will be formed and the associated frame rail. Those parts may be pressed on a surface of the metal plate opposite to the surface of the leadframe on which the chips will be bonded. Then, the convex portions to be the lands can be easily formed just as intended.
In still another embodiment, the convex portions may be isolated in the step d) from the die pads by cutting off the respective parts of the internal inner lead portions located between the convex portions and the die pads using cutting means. Then, the convex portions can be isolated from the die pads easily and the lands can be formed as the convex portions that are isolated from each other.
In this particular embodiment, the cutting means preferably has a cut face, which is substantially parallel to respective upper surfaces of the convex portions and the die pads. Then, no burred portion will be formed around the convex portion, for example. Also, if the joining/supporting members are cut off by a punching process like this, then some debris will be made. However, if the debris is received by the lead retaining member, the debris will not affect the manufacturing process.
In yet another embodiment, the lead retaining member may be chemically dissolved and removed in the step g) or i). Then, the lead retaining member is removable non-mechanically, thus simplifying the manufacturing process.
In yet another embodiment, the leadframe may be cut off with a dicing blade in the step j). In such an embodiment, even if the leadframe includes multiple die pads, the leadframe can be easily divided for respective resin-molded semiconductor devices (or packages).
A second inventive method for manufacturing a resin-molded semiconductor device includes the step of a) forming frame rails, multiple sets of inner lead portions and die pads out of a single metal plate. Each said set of inner lead portions are supported by a first group of joining/supporting members that extend inward from the associated frame rail and are joined together by a second group of joining/supporting members. The method further includes the step of b) forming convex portions on a surface of the inner lead portions so that the convex portions are spaced apart from each other. The surface is opposite to an upper surface of the die pads on which semiconductor chips will be bonded. The method further includes the step of c) placing a lead retaining member on respective surfaces of the inner lead portions and the frame rails and thereby getting the inner lead portions and the frame rails retained by the retaining member. The surfaces on which the retaining member is placed may be either the same as, or opposite to, the upper surface of the die pads on which the chips will be bonded. The method further includes the step of d) removing, from at least some of the joining/supporting members of the second group for the inner lead portions, respective parts thereof located between adjacent ones of the convex portions or between one of the convex portions and the associated die pad that are adjacent to each other, thereby forming inner leads that have been selectively isolated from the die pads and obtaining a leadframe with the lead retaining member. The method further includes the steps of e) bonding the chips onto the upper surface of the die pads of the leadframe; and f) electrically connecting the chips to the isolated inner leads using metal fine wires. If the lead retaining member has been placed on the surface of the leadframe on which the chips have been bonded, the method further includes the step of g) removing the lead retaining member from the surface of the leadframe on which the chips have been bonded. The method further includes the step of h) molding the chips, the die pads and the inner leads together with a resin encapsulant so that the convex portions of the inner leads have their top exposed. If the lead retaining member has been placed on another surface of the leadframe opposite to the surface thereof on which the chips have been bonded, the method further includes the step of i) removing the lead retaining member from the opposite surface of the leadframe. And the method further includes the step of j) dividing the leadframe, along with the members assembled thereon, into multiple packages so that each said package includes at least one of the chips.
According to the second inventive manufacturing method, the second inventive resin-molded semiconductor device can be formed just as intended by using the second inventive leadframe.
In one embodiment of the second manufacturing method, the convex portions may be formed in the step b) by etching away a part of each said joining/supporting member of the second group. The part to be etched may be located either between the parts of the associated inner lead portions where the convex portions will be formed or between the part of the associated inner lead portion where the convex portion will be formed and the associated die pad. Also, the part may be etched away from a surface of the joining/supporting members of the second group opposite to the surface of the leadframe on which the chips will be bonded.
In an alternative embodiment, the convex portions may also be formed in the step b) by pressing a part of each said joining/supporting member of the second group. The part to be pressed may be located either between the parts of the associated inner lead portions where the convex portions will be formed or between the part of the associated inner lead portion where the convex portion will be formed and the die pad. Also, the part may be pressed on a surface of the joining/supporting members of the second group opposite to the surface of the leadframe on which the chips will be bonded.
In yet another embodiment, a part of each selected joining/supporting member of the second group, which part is located either between associated ones of the convex portions or between associated one of the convex portions and the die pad, may be cut off in the step d) with cutting means, thereby isolating the convex portions from each other or from the die pad.
In this particular embodiment, the cutting means preferably has a cut face, which is substantially parallel to respective upper surfaces of the convex portions and the die pads.
In yet another embodiment, the lead retaining member may be chemically dissolved and removed in the step g) or i).
In yet another embodiment, the leadframe may be cut off in the step j) with a dicing blade.
A third inventive method for manufacturing a resin-molded semiconductor device includes the step of a) forming frame rails, multiple sets of lands, multiple sets of inner leads and die pads out of a single metal plate. Each said set of lands are supported by joining/supporting members extending inward from the associated frame rail and are joined together so as to be spaced apart from each other. Each said set of inner leads electrically connect some of the lands together. And each said die pad has an upper surface on which a semiconductor chip will be bonded. The method further includes the step of b) placing a lead retaining member on respective surfaces of the lands and the frame rails and thereby getting the lands and the frame rails retained by the retaining member. The surfaces on which the retaining member is placed may be either the same as, or opposite to, the upper surface of the die pads on which the chips will be bonded. The method further includes the step of c) removing, from at least some of the joining/supporting members, respective parts thereof located between adjacent ones of the lands, thereby selectively isolating the lands and obtaining a leadframe with the lead retaining member. The method further includes the steps of d) bonding the chips onto the upper surface of the die pads of the leadframe; and e) electrically connecting the chips to the isolated inner leads using metal fine wires. If the lead retaining member has been placed on the surface of the leadframe on which the chips have been bonded, the method further includes the step of f) removing the lead retaining member from the surface of the leadframe on which the chips have been bonded. The method further includes the step of g) molding the chips, the die pads and the inner leads together with a resin encapsulant so that the convex portions of the inner leads have their top exposed. If the lead retaining member has been placed on another surface of the leadframe opposite to the surface thereof on which the chips have been bonded, the method further includes the step of h) removing the lead retaining member from the opposite surface of the leadframe. And the method further includes the step of i) dividing the leadframe, along with the members assembled thereon, into multiple packages so that each said package includes at least one of the chips.
In the third manufacturing method, the lands and frame rails are retained by the lead retaining member on their upper and/or lower surface(s). Accordingly, even if a leadframe, including not only the lands but also the inner leads for electrically connecting some of the lands together, should be used, neither the lands nor the inner leads will drop off from the frame rail. Thus, a small-sized leadframe, including lands arranged in multiple rows, can be easily made out of a single-layer metal plate.
In one embodiment of the third manufacturing method, the step a) may include the step of forming the inner leads out of the joining/supporting members between the lands by etching away respective parts of the metal plate from a surface thereof, on which the chips will be bonded, to approximately half the thickness of the metal plate while masking other parts of the metal plate that will be respective center portions of the lands extending in parallel to the associated joining/supporting member and also masking still other parts of the metal plate that will be the inner leads located between the associated lands. And the step a) may further includes the step of etching away yet other parts of the metal plate from another surface thereof, opposite to the surface thereof on which the chips will be bonded, with the parts of the metal plate to be the lands masked on the opposite surface so that the lands and the inner leads are isolated from each other.
Then, each of the lands will have a cross-sectional shape with an upwardly decreasing width and each of the inner leads, formed between adjacent lands, will have its top positioned approximately as high as that of the lands and its bottom positioned higher than that of the lands. Thus, the third inventive resin-molded semiconductor device can be formed just as intended.